Air impeller housing



s Sheets-Sheet 1 w hm, Q

F. c. LINDVALL ETAL AIR IMPELLER HOUSING R. kw

,jnvenz arzrd MN .QNNV lml UNN/ June 3 1948.

Filed Sept. 4, 1945 llllluu lllllllhq hhi lllih 5 m 1, 394%. F. c. LINDVALL ETAL AIR IMPELLER nousme 3 Sheets-Sheet 2 Filed. Sept. 4, 1945 Int/"E17 2 2712- Paul K BEEmEZ-' F. C. LINDVALL ET AL June 1, 1948 AIR IMPELLER HOUSING 3 SheetsSheet 3 Filed Sept. 4, 1945 Invenzaz? rick E.L2'.'z7dvall Jan] K255 12752 .Fau] flat]?- 05775557 I Freda Patented June 1, 1948 omTEoi- STAT-ES OFFIC. 1

2,442,42c" AIR IMPELLER'HOUSING i Beemer, Inglewood,

gom'ery, Chicago; 111.,

Altadena, and- Palil K.

porated,-Los Angeles,- Califz; a corporatiomof California Application September 4, 1945-,SerialNb; 61452.20

10 Claims. c. This; invention relates to improvements inair irnpelier orfan'housingsand in metho'dsof constructing them. The invention relates m'ore par ticularly to the :structure'and fabrication of inipelljer=housings ofthe general type showfl'in- 'the van Dorn Patent'No: 2,349,315;- May 23,1944.

Impeuer': housingsof that type embody; an elonga'te' box-like structure *of'sheet metal, with top and-floottoni walls' and-discontinuous or "sectional sidewalls? The side wall sect'ions along opposite sides-arerelaitively" staggered along 'the'length of the box; and transversepartitions join the sidewall-sectionsinsuch 'ma'nnerasto-form chambers which; proceeding along the length of I the box, ope 'u t alternately to "opposite sides of the box. Th 7 everal'partitions-have central circular openin which-are alined one central longitudinal axi'syan'da single drive shaft extending through the box onthat axis carries air propeller'fans in alternate chambers, that is, in the" chambers wlii( :i 'ifope'i'r out to one side of the box.

Difficulties havebe'en found in fabricating such a housing inexpensively and in" providing a nuished' structure which at" the same time is suffici'ently strongand rigid to take *thestatic'loads and shockqoa'ds to which the structure is sub jecftedj'inu'se; without distortions that will throw the shaft bearings out of 'alin'ement, those bearingsbein'ginounted on the'structure. Previously it"has been the practioeto'fiangethe' various components and to "weld them together either by manual arc or 'spotw'elding. That fabrication has'previdedf or ample' rigiditybut has beenrelativeiy slow and expensive, due largely-to the fact that the Welding points have necessarily been? located in difierent'situations' where no single and simple repetitive'welding operation could be expediftioiisly applied.

It isoiie of the features of the present improve- Irirlt that "the entire Operation of Securing the component parts together involves nothing but the repetition of a simple operation applied only to the top'and bottom faces of the structure. The securing points are easy to reach and the securing operation is very simple.

Another feature ofthe present improvements" lies "irith'fact that-the general design, and that of the'seur'ings, are such thatiullyw'elded conmotions are not necessary, connections of a forged 'riveted'or headed type giving ample rigidity tothefinished structure. Temperatures need not be as highas requiredfor' true welded connections and danger of burning the 'thin sheet metal isfavoided. And a further feature isintheprovision of mounting plates, for the shaft bearings,-

which are secured in the :structure in. thesame manneras the transverse partitions and side walls,- serve to further stiffen the structure, and requireonly repetitions of-thesame simple secur- 5 ingoperations cedures-embodying the invention; reference for the purpose of such description beinghacl to the accompanying' tlra'wings, in-which Fig. 1 is a plan with part of the top'plate broken-away, showinga housing structure typical of the invention} Fig. 2 is an enlargedfragmentary plan of the structure shownin *1, without the top plate;

Fig. 3 is a plan of the corresp'ondingportion of the top plate;

Figwi -isa vertical cross sectiontakenas indicated by' line 4 -4 -on- Fig. 2, showing the top plate inpla'ce-and; the parts assembled ready for the securing operations;

Fig. '5 is a similar section on-line 5 -5 or"- Fig. 2

Fig; 6 is'a fragmentary plan-section ofpar-ts corresponding tothose shown in Fig. 2 but-show ing the" complete assembled impeller unit;

Fig?! is-a cross section online-l -'i of Fig. 6; Fig.-- 8 is a cross section on line 8-8 of Fig. 6; Fig.9 is an enlargeddetailsectionshowingone unit of the securing means assembled ready for the final securing operation;

Fig. 9a is 'a'similar view showing another unit of the securingmeans;

Fig... 10 is'asection on line l 3==l 0 of 9;-

of a plate which forms-oneelement of'the securing .unit' of Figs. 9, 10. and 11';

40 Figsj13 and learesections similar to those'of Figs. 9" and 10 but showing the parts as they appear afterthe final securing, operation;

Fig. l3a 'is a-vi'ew similar to that of Fig."13,but showiii'g'the securin'g'unit'of Fig. 9a;

Fig. I5 "is an enlarged vertical longitudinalsection'on line l5 -l5 of'Fig. 7

Fig. 16 is an end-elevation of suitable apparatus on whi'ch the repeatedsecuring operationsare readilylperformed; and

Fig.' 1'7 is an enlarge'd d'etail section on line II -I'I of Fig; 16.-

As shown 'illust'ratively inthe drawings, the cas-' ingiscomposefimainly of bottom plate 28.; top

plate 21'; and'verti'cal plate" units 221which provide both the sectional side Wall units 23 and;

Fig. ll is' aplan ofthe parts shown in Figs.-

the transverse partition units 24. All these parts, and the bearing mounting plates 38, are composed of relatively thin sheet metal. To give an idea of relative dimensions, a housing about 96 inches long and with a transverse body dimension of about 8 inches, is constructed entirely of sheet metal 0.105' inch thick. As is seen in Figs. 1 and 2, the side wall sections and the transverse partitions make a formation, in plan, which may be described as being rectangularly sinuous. The formation is such that the several side wall sections 23 and partitions 24 may be formed of a single long sheet of metal bent to the desired conformation and provided with the apertures and tabs which will be described. And accordingly the several vertical plate units 22 may be considered as collectively forming one long sinuous unit which includes all of the side wall sections and the transverse partitions. However, we prefer to make up that long unit of a plurality of duplicated units, such as the units 22, because of the manufacturing complications involved in making the single long unit with the accuracy which is required of that unit to fit the other parts. The single long unit cannot be produced in one operation, whereas the small duplicated units can be simply produced by die pressing. Ihis subdivision into short duplicate units also facilitates the provision of drainage openings, as will appear.

Accordingly, the side wall sections and partitions are provided by a series of units 22, each of which is rectangularly U-shaped in plan. These units are assembled in the configurations shown in Figs. 1 and 2, and in the final assembly are preferably separated by the slight vertical gaps shown at 25 in Fig. 2. While the several units might tightly abut at 25 at their meeting edges, slight gaps at those meeting edges provide convenient drainage escapes for Water which might otherwise collect at one side of the casing. As shown in the issued patents previously referred to, these impeller casings extend transversely across the car floor, and unless some facility is provided for drainage of water past them, water from a car loading may bank up against one side of the casing. The provision of the drainage openings, easily provided by the gaps between unit 22, allows such water to pass the casing to find an outlet.

Although the several U-shaped wall units 22 may be full duplicates of each other, we prefer to make the units 22 which lieat one side of the casing a little wider than units 2211 which lie at the opposite side of the casing. All units 22 are full duplicates and all units 22a are full duplicates. The resulting formation is such that the chambers 26 which are open at one side of the 'casing are somewhat wider than chambers 21 which open at the opposite side of the casing. The wider chambers 26 are the ones which take the impeller fans, as will be described.

As shown in the drawings, the complete sinuous wall unit, made up essentially of units 22 and 22a, also includes a pair of end units 22b which, instead of being U-shaped, are L-shaped, and are composed of a partition section 24 and a short side wall section 23a. The standard and duplicated unit 22 and 22a, are made up of a side wall section 23 and of two partition half sections 24. Each partition, when the parts are assembled, is thus made up of two half sections; Each partition has in it a circular opening made up of two semi-circular openings 30 which are formed in the two half sections 24. This cir- ,4 cular opening is flanged at 3| to stiffen the partition members, and to provide smooth and efiicient air flow through the opening into the center of the fan.

To make the structure of Figs. 1, 2, etc. more intelligible, we refer now to Figs. 6, 7 and 8, which show the structure and arrangement of the complete finished impeller unit. As shown in those figures, the wider chambers 26 accommodate impeller fans of the radial blade type, such as shown at 35. These fan units are set on their single longitudinal shaft 36 which extends centrally longitudinally of the housing structure and is mounted in bearings 31 which are carried on vertical bearing plates 38 located in some of the narrower chambers 21 and, in one instance, located in the end space within one of the end units 231) (see the right hand end of Figs. 1 and 6); 'These'bearing plates 38 are mounted on and assembled With top and bottom plates 2| and 20 in the same manner that units 22 are assembled with those plates, so that the bearing plates become a rigid part of the finished structure, help to stiffen it, and maintain a rigid relation to the partition walls of the structure and to each other. The bearing plates are shown in Figs. 4 and 7, and Figs. 6, 7, and 15 show the mountings of the bearings 3! on those plates. The bearings proper are shown as ball bearings 40 mounted on shaft 36. The outer members of these bearings 40 are mounted in' internally grooved rubber rings 4| which have external grooves fitting interiorly into a flange 42 of a bearing base plate 43. Each bearing mounting plate 38 is provided with a central opening 44 of suificient size to accommodate ring 4| with clearance, and each plate 38 is also provided with a pair of slotted bolt openings 45 which are elongate'in one direction, say vertically. Each bearing base plate 43 is provided with registering bolt holes 46 which are elongated horizontally. The arrangement provides for easy adjustment of all the bearings 31 in axial alinement on the finished and rigid housing structure, thebolts 48 being set up when that alinement has been adjusted Ears 49 are turned down against the bolt heads before setting up the nuts, and the latter are locked with an ordinary lock washer. When finally set in position, the several bearings are rigidly secured to their several mounting plates 38. And, as will be seen, our invention provides a structure in which the several bearingplates 38 are rigidly maintained in alinement with each other and in alinement with the other parts of the structure. Freedom of the bearings for angular alinement is allowed by the rubber rings 4 I.

The narrowerichambers 21, in some of which the plates 38 are mounted, provide the chambers or passages by which air enters the .casing from one side, the air then passing through the partition openings 38 endwise into the impeller fans, and then being thrown out at the opposite side of the casing by the rotary action of the impeller fans.

Going back now to Figs. 1, 2. and 3 we Will'eX- plain how the various wall units of the casing, and the bearing plates 38, are assembled and secured in a rigid assembly. Each unit 22 is provided, along its top and bottom edges, with a series of spaced, projecting, rectangular tabs 50, arranged in plan as is bestshown in Fig. 2. At the edges which meet or form the gaps at 25, each of the units is provided, on the top and bottom'edges of its partition sections-24, with projectin tabs 5! which are only half the Width all =-i it -ar .r iiplioot o-a rt s z endo and thesame is true of all the tabs n i I -thoaoso h fi rmo sho in Eggs. 1; and- 2,:;the several projecting-tabs of all h .es iohlo qon t orm a. c rta e in p t i o th toe-en bo o ed e of t ea sem t m etin m ntin .p o 3. a r de at hei o ae hott medges with h s ona 1 tia o ziho t bs. z the final asse .bear a 1 o to o a ionohi i l o hop wt r o the the tab il3i th1.t... ;bot om fin -2 01 1 Plates a )1 QYidd with perforations {it arranged on the sepably,,;patter n of tabs to and El and thus daptedqto take andpassthe-several tabs '56 and @Shwqhenthaparts are assembled. Perforations fii a e all. of duplicate-size, a little larger than the ossesectional size of tabs 55. Thisincludes :.t e pertorations 55a eachef which take a pair goflthahalf-siaedtabsil. Fig. 3 maybe under- ;.;s, t ood;to show'the pattern arrangement of the. .p.erfor ationsin-both bottom andtop plates 20 -.-ae .-2 l

: gs. v9.to. l 2 show in enlarged detail the pre- ..;f =e forrnation of the tabs and perforations and .thei elationship toeach other when initially assembledandready for the securing operations. 'l 'hese figuressshow a.;plate,; for instance the half portion -plate24r. with. a tab 58 projecting through on opening- 5; in top plate 2!. The illustrations are;-howevertypicalof all tabs 59 and their re- ...ceivingperforations. Thespecial openings 55a hicli-tal;e the half tabs 51 are shown in Fig. 9a in;the ir initially assembled positions, and in Fig. l mi in -their finally secured conditions.

ASiShQWH in Figs. 9 to 12, the top plate 21 (and li l;ewise;bottom-plate 2!!) is exteriorly recessed around;each opening 5'5, preferably with a recess :;,60- Which=is. -circu1ar in plan. The diameter of this external recess is preferably slightly larger thanthe length dimension of opening 55. The recess is; f-ormedbypressing the sheet metal in- ;waigdly,. in the same die pressing operation by which openings 55 are. formed. Ihe recessing ,..operation .of course results in a corresponding conve xprotuberance ti on the inner face of the -sheet metal plate or 2!, which protuberance hasfl .a; diameter somewhat larger than the length r,d-irnension.ofperioration slot-55. And, in order to allow the-edges 62 of the vertical plates 23, 24, .etc; to li e directly against the inner faces of the top andbottom plates, the areas at 63 on the innertaces of the top and bottom plates which w.o uld;otherw-ise project slightly inward of those innerfaces, are left flat in the same die-pressing eneration-tote flush with those inner faces. The .igesulting, inner iace formation is shown in Fig. 12 .wherethe pertorationslot 55 is shown to have a glessthan semi-circular bulge at each of its longi- ..tud,ina1 edges, but no bulge exists at its end edges. 5A5 arresu-lt of the described formation, the hpper andlower edges of all the vertical plates ..or ;s heets are-allowed to abut the inner faces of ether top and bottom sheets, and the opposed straight-edges 65a of the bulges 6! overhang the edges of-thevertical sheets on each side. Tabs .fifl prfoject through the openings 55 and upwardly throug-hiand-beyondthe recesses 5t. Proportion- .ate. dirnensionswhich have been found suitable .ahjirptaotioable for the assembly are shown in 5131365231 41536dgdtitilfigllres; although of course the s sh dj stm tt nsmi s invehtionyi not =.t .b 1 imited t he particul pr ti i l s ate Fiafio shows how :t oisom -ta s 5 l -=fit intqand t rou htheyeriora n fiia; wh-ioha eidontio l w t an ro e d: in th samoam 'cno as h rrorations- 5 iwhona h parts ar nitially-assemth p12 ex s in aho woo th two Y partiti n o tions l an A Woon th two .s .mi.-tabs':;.5 l.

o m no omp r fea e nort s 1 .1 hat.

when themar u ro ni ia ssombl mtho g p z ar edov z hoto rh tt mn atoon-ask eto blyypositions with a ll of their .-l I I H i s w w r l t ro s fih oo rrosoo l e. e

fcrations. Then the other top or bottom;, ;p,l ate is oe 1o t o-th s m l -r o ti at unit a "l f-the upper Snob as em i id o to i Blood. a on v shown.inythesectional ;ViQWS QffFigS. and 5. h --Wh a s b i x on oo yi o securing operations ch B0ll$ 111jf theyarious parts into one-m structui3e.

n their n i l -.-osoo.mhlo .qoa oaeaoi-tab o hi hro f i ot thro a counter-part tab direotly-ver ,i io ine th ou h-bott m 331M161 hlo i i ha it x EigsiA and 5 ii ste z show ho g h tab z saadet :o v rtioo :uo t vi an 13: a arran ed 'opposi each other ,at the topand= bottom-;edges of; those units. And, -as-stated, the-patterns'of perforations in the top;ahdbottom -plate ane tha ame.

. on oqoo fiy oo :t which p o ects a ooveithe up sor oeof h i ally assem d. structu sa one. ta din ot yo po it itprosembled structure and than arrangementgreatly facilitates the final securing operations. And

all of these opposed pairs; of tabs are.- substantial p o osxo o th .t eon1y--; ifierenceheine that the special tabs lal 'are, 'oefiectitWQ parts which together make Hi! all npo ite tab. which is -;subs,tantia-lly like a tab fgfl. That substantial duplication which exists throughout all of. .thetab s oo th i ra ihata of. thaioa rs .ofitabs ihave a commonpositional relation-tothe wholeassemblyfimake it possible to perform thefinalsecurementby simple repetition of'a simplasecuringoporation.

Generally. described, the; final :securing, opera- ,tion consists in simultaneously rand oppositely p resslng and heating each-pair of. projecting tabs.

A suitable apparatus for perf orming the operaapparatus of the-electric weldin typegis provided,

ing heads T l mounted: in-the frameone above. the

other. Acarriageilis; provided toccarnyithe: initially assembled unit whichis designated 'by. the

-letterU in :Fig4l6 and shownto betsupported in position-between .thetwo heads H. Carriage I2 is mounted on 120118131 8 on. asuitable base .14 in .suchpa mannenthat Ethecarriage canzhe moved -=transversely 10f its: length rand iof-ithezlengthsof unit U;.and the unit U is movable longitudinally of its length (normal to the plane of the drawing in Fig. 16) by sliding along the length of the carriage or by moving on transverse rollers 13a with which the carriage may be supplied. The arrangement has the result of allowing unit U to be easily moved either longitudinally or transversely with relation to the opposed heads 1|, and of being constantly maintained in such orientation that when any upper projecting tab is brought under upper unit H, the lower corresponding and opposite tab will be brought directly over the lower unit 1|. With a pair of tabs in such positions, the two units 1| are operated simultaneously to perform the final securing operation on that pair of tabs.

Details of a suitable operating head for performing the securing operation are shown in Fig. 17. As there shown, the head includes a relatively stationary member lawhich has in it a cylinder 16 taking a plunger 11. Plunger 11 is moved longitudinally (downwardly in Fig. 17) by admission of fluid pressure at 18. A pair of springs 19, seated upon lugs 86 which project from member 15, and acting on vertical studs 8| which move with plunger 11, are adapted to return the plunger to the normal position shown in Fig. 17 when the fiuid pressure is relieved. Studs 8| are connected with ears 82 which are formed as extensions of plunger 11. The studs are connected to ears 82 in such a manner that the studs cannot move upwardly with relation to plunger 11 as for instance by having collars 83 under ears 32.

Studs 8| project downwardly below collars 83 and at their lower ends they carry a presser foot member 84 slidable upon them. The presser foot member is supported by nuts 85 at the lower ends of studs 8| and is pressed down on the studs by a pair of springs 86 confined between foot member 84 and collars 83. The presser foot has a central vertical opening 86 and has a lower annular foot 81 which is adapted to seat on the work with a pressure which is determined by the strength of springs 86. When plunger 11 moves down, foot 81 moves down with it until the foot seats on the work, and then further downward movement of the plunger applies the pressure of springs 88 to the work.

A cylindric electrode 96 is carried in an adapter 9| which is mounted on the lower face of plunger 11 with interposed insulation 92. An insulating sleeve 93 also surrounds adapter 9| where it passes into and through opening 86 in foot member 8 In the normal position of the parts electrode 90 lies with its end somewhat inward of the end of foot 81. When pressure is applied to plunger 11 the first operation is to move foot 81 into contact with the work under the pressure of springs 86. During further movement of plunger 11, and as electrode 90 is moved into contact with a tab, the presser foot is maintained against the work under the spring pressure. That foot pressure is thus maintained constant while the pressure which may be applied directly to the electrode and to the tab depends upon the fluid pressure which is applied to plunger 11. That electrode pressure is sufiicient to press and forge the tab when the tab is heated to a suitable temperature by the applied current.

The preferred relationship of size, between a tab and its surrounding recess, and pressure foot 81 and electrode 90, is indicated in Fig. 17. As there shown, the internal diameter of annular foot 81 is larger than the diameter of the recess 60, and the diameter of heating and pressing electrode is also preferably somewhat larger than the recessed diameter, so that the electrode may finally seat on the normal flat surface of the top or bottom plate of the assembled structure at the end .of a securing operation rather than seat in the recess 60. With this provision the tabs can be forged down and flattened to a condition flush with the outer surfaces of the plates, but the head which is formed on the tab cannot easily be reduced in thickness to a dimension less than that which is determined by the depth of recess 60.

The two operating heads 1| are duplicates and are operated simultaneously to apply their pres sure feet oppositely to the assembly, and to apply their electrodes simultaneously and under equal pressures to the two opposite tabs of a set. When the electrodes are thus applied the heating current flows in series from one electrode through its contacted tab, and then through the immediately associated plate and the assembled structure in general, to and through the other contacted tab and the other electrode. The heating current and forging pressures are thus applied simultaneously to the two opposed tabs of a pair. Fig. 16 shows, merely diagrammatically, a piping system I00 for applying fluid pressure simultaneously to both heads 15 under control of a single valve which is indicated at H31; and also shows diagrammatically the connector strips I62 which connect severally with the electrode adapters 9|, and the circuit IE3 in which the connectors I02 and the electrodes 96 are connected in series. In an actual practical embodiment of the apparatus, the arrangements are such that foot valve I (H can first be operated to apply the fluid pressure to the heads to first bring feet 81 into opposing contact with the work, and then move the electrodes into pressure contact with the work. Further actuation of the foot device then initiates the electric heating cycle. The electrical circuiting and control are such that the heating current is not applied, to the circuit until the circuit is first closed by the electrode making initial contact with the tabs, and the current is then automatically cut off after a time period suificient for the heating and forging operation to be completed. Such details however need no illustration or description here, as they form no part of our present invention. In fact We make no claim here to the apparatus of Figs. 16 and 17 in and of itself, only making claim to it as a part of certain method combinations and as involving means for performing the operations which are described.

The finished securings are illustrated in Figs. l3, l4 and 13a. Figs. 13 and 14 show the finished headed form which is taken by a tab 59, and Fig. 13a shows the finished headed form taken by a pair of semi-tabs 5!. As shown in Figs. 13 and 14 the heated tab expands transversely in both planes, expanding so as to fill the length of perforation 55 at least in the outer .part of the perforation. This expansion is illustrated in Fig. 13 at 50a. The outermost part of the tab also expands in the same direction to form at least a slight heading at 5912 beyond the ends of perforation 55. In the direction crosswise of perforation 55 the tab expands laterally, as indicated at 500 to fill at least the outer part of opening 55. That expansion may extend inwardly of plate edge 62 to fill more of the aperture, but not necessalily so. And outside of the aperture 55, in the recess 66, the tab expands laterally to form a con siderable head as shown at 50d. It is not necessary that the heating current be large enough and the-temperature be carried hi-gh enough to cause welding to-takeplace between the-parts which are '-forced into heated contact By carrying the temperatures suficiently high, welding may take place" to some extent, after the-tabs have-been expanded into contact with-the plate. But such weldingis-not necessary; It is sufii cientthat the tabs-be forged into rivet lika heads which comfill the aperturesand which pletely and tightly the externalsurface of the head tightly over plate. The plate is then 'held '-in solid and tight enga'gement with the edge or the; wall member; such 41524}- and when this tight holdin-g secure ment has been performed for'all' ofth'e several sets of tabs onthe' longitudinal side iwalls and the transverse partition walls and the transverse bearing" mounting plates; the whole structure is then so rigidly interconnected that; although it 13a the final form is the same as that shown-in Fig;--l3,-and thesame numerals are applied,- except th'atthecuterparts of" the= -two half-tabs are forced togethen at b, and may be partiallyweldedthere or areat least integratedso that the resultant integrated whole head is inall essentials like that shown in Fig. 13'. To provide the metal for forming the juncture at till), the tabs 5| may initially be a little'higher thantabs 50' *butthose tabs -5 l are-in practice-made ofth'e same height as tabs 59, and the metal for forming that juncture is taken from the lateral overhang of the head (shown in Fig. 14) so that that lateral overhang in the case of tabs 5! may be slightly less than it is for tabs 56.

We claim:

1. An air impeller casing composed of sheet metal, comprising an elongate lower wall plate, an elongate upper wall plate, an intervening vertical wall plate unit contacting the lower and upper plates at its lower and upper edges, said vertical wall unit having a configuration in plan which is substantially rectangularly sinuous and extending longitudinally of the lower and upper plates, and said vertical wall unit forming a series of longitudinally arranged chambers between the lower and upper plates which chambers alternately have open sides at opposite sides of the casing, and a series of substantially identic securing units spaced along the upper and lower edges of the sinuous vertical wall plate unit, each of the substantially identic securing units co--- prising an integral tab projecting from the edge of the vertical plate through the upper or lower plate and headed over the external surface of that plate.

2. An air impeller casing composed of sheet metal, comprisin an elongate lower wall plate. an elongate upper wall plate, an intervening vertical wall plate unit contacting the lower and upper plates at its lower and upper edges, said vertical wall unit having a configuration in plan which is substantially rectangularly sinuous. and extending longitudinally of the lower and upper plates, and having alternating side wall sections and longitudinally spaced transverse partition sections connecting side wall sections at opposite sides of the casing, and a series of substantially identic securing-units spaced along the-upper and lower'edgesofthe sidewall sections and the partition sections;- each-oi the "substantially identic securing units comp'risingan' integral tab projecting frOm'theEedge-Qf'the' vertical wall unit plates; and 1 having alternating'side" wall se ctions' and :longitudi'n'allyspacedtransverse partition sectionsconnecting side wall sections at opposite sides -of the :casing; and -a series of substantially: identic'securingunits-spaced along the upper and lower edges of thei'side w'al'l "sectionsand thepartition "sections, each of" the substantially identic securing. units comprising an integral tab project-ing from-the; edge of the vertical wall unit 2 through an aperture in the adjacent plate-,.the plate being externally recessed'aboutthe aperture'and having internal recess'bulges which lie at oppositesides of the plate edge, andithe' tab being headed over. the, externalsurfa'ce of the plate in the recess;

4'. An impeller casing composedlof sheet-metal,

comprising an elongatelower wall plate; an elongate upper-iwalhpljate; an intervening vertical wall 'plate unit contacting the lower; and Lupp'er plates at its "lower ahdupper. edges, said: vertical wall unit having aconfig'uraticn in planiwhich isl.

substantially 'rectangularly'sinuous and extending longitudinally of the lower and upper plates, and having alternating side wall sections and longitudinally spaced transverse partition sections connecting side wall sections at opposite sides of the casing, a plurality of transverse vertical bearing supporting plates arranged in some of the spaces between adjacent transverse partition sections, said bearing supporting plates having their upper and lower edges in contact with the upper and lower plates, and a series of substantially identic securing units spaced along the upper and lower edges of the bearing supporting plates and the side wall sections and the partition sections, each of the substantially identic securing units comprising an integral tab projecting from the edge of the vertical wall unit through the upper or lower plate and headed over the external surface of that plate.

5. An air impeller casing composed of sheet metal, comprising an elongate lower wall plate, an elongate upper wall plate, an intervening vertical wall plate unit contacting the lower and upper plates at its lower and upper edges, said vertical wall unit having a configuration in plan which is substantially rectangularly sinuous and extending longitudinally of the lower and upper plates, and having alternating side wall sections and longitudinally spaced transverse partition sections connecting side wall sections at opposite sides of the casing, a plurality of transverse vertical bearing supporting plates arranged in some of the spaces between adjacent transverse partition sections, said bearing supporting plates having their upper and lower edges in contact with the upper and lower plates, and a series of substantially identic securing units spaced along the upper and lower edges of the bearing supporting plates and the side wall sections and the partition sections, each of the substantially identic securing units comprising an integral tab projecting from the edge of the vertical wall unit through an aperture in the adjacent plate, the plate being externally recessed about the aperture and having internal recess bulges which lie at opposite sides of the plate edge, and the tab being headed over the external surface of the plate in the recess.

6. An air impeller casing composed of sheet metal, comprising an elongate lower wall plate, an elongate upper wall plate, an intervening vertical wall plate unit contacting the lower and upper plates at its lower and upper edges, said vertical wall unit having a, configuration in plan which is substantially rect'angularly sinuous and being composed of a plurality of substantially identic sub-units mutually spaced at their adjacent edges to provide drainage passages, and a series of substantially identic securing units spaced along the upper and lower edges of the sinuous vertical wall plate unit, each of the substantially identic securing units comprising an integral tab pro- J'ecting from the edge of the vertical plate through the upper or lower plate and headed over the external surface of that plate.

7. An air impeller casing composed of sheet metal, comprising an elongate lower wall plate, an elongate upper wall plate, an intervening vertical wall plate unit contacting the lower and upper plates at its lower and upper edges, said vertical wall unit having a configuration in plan which is substantially rectangularly sinuous and being composed of a plurality of substantially identic sub-units arranged in substantially abutting relation at their adjacent edges, and a series of substantially identic securing units spaced 12 along the upper and lower edges of the sinuous vertical wall plate unit, each of the substantially identic securing units comprising an integral tab projecting from the edge of the vertical plate through the upper or lower plate and headed over the external surface of that plate.

8. An air impeller casing as defined in claim 1, and in which the upper and lower securing units on the vertical wall plate unit are arranged in vertically opposite pairs.

9. An air impeller casing as defined in claim 6, and in which the upper and lower securing units on the vertical wall plate unit are arranged in vertically opposite pairs.

10. An air impeller casing as defined in claim 7, and in which the upper and lower securing units on the vertical wall plate unit are arranged in vertically opposite pairs.

FREDERICK C, LINDVALL. PAUL K. BEEMER. PAUL H. MONTGOMERY.

REFERENCES CITED The following references are of record in the 

